This research addresses the major global health challenge of preventing HIV infection among labor migrants. It focuses on men from Tajikistan, Kyrgyzstan, Uzbekistan, Ukraine, and Moldova who have come to work in St. Petersburg, Russia. This study aims to build scientific knowledge on the multilevel risks associated with labor migration that can lead to HIV infection as well as the spectrum of involvement in HIV prevention and care among labor migrants. The clinic-based case-control and mixed methods design integrates biomedical, survey, and ethnographic methods. The knowledge generated will inform the development of more targeted and effective strategies for HIV prevention, testing, and linkages to care for labor migrants. The specific aim are: 1) to quantitatively investigate the associations between HIV infection and multilevel determinants related to labor migration at the levels of social policy, sociocultural practices, health and mental health, and sexual practices through a clinic-based case-control design; 2) to qualitatively investigate the spectrum of involvement in HIV prevention and care among labor migrants (including experiences and perceptions regarding HIV testing, HIV infection, linkages to care, barriers to care, and the impact of labor migration) through minimally structured interviews of a purposive sample of HIV infected migrants, non-HIV infected migrants, providers, community advocates, and policymakers. Aim 1 will be accomplished through a survey of 200 HIV positive Central Asian male migrants and a matched sample of 200 HIV negative Central Asian male migrants. Aim 2, will be accomplished by conducting ethnographic interviews with a purposive sample of HIV infected migrants (n=12), non-HIV infected migrants (n=12) drawn from the larger sample, as well as providers (n=6), community advocates (n=6), and policymakers (n=6). The knowledge generated will lead to the development of more targeted and effective strategies for engagement in HIV prevention, testing, and linkages to care for labor migrants.